This invention relates to a friction brake shoe assembly and method of producing same, and more particularly, to a brake shoe assembly usable for motor vehicles which includes a perforated metal backing plate having raised tabs onto which friction material is cast.
Drum type friction brakes include brake shoe assemblies which are typically urged into contact with an inner cylindrical surface of a rotating brake drum by a hydraulic actuating cylinder. Various approaches to attaching the friction material, typically asbestos based, to the metal shoe or to a separate backing plate have been previously employed or proposed. Generally speaking, two major types of fastening system are currently employed. In one type of system, a pre-formed segment of friction material is bonded by adhesives to the metal brake shoe or to a backing plate which becomes attached to the brake shoe by mechanical fasteners. Another major type employs mechanical fasteners such as deformable rivets which are placed at a plurality of locations on the surface of the friction material and engage bores in the associated brake shoe or backing plate, thereby fastening these parts together. Irrespective of which of the above systems are selected for manufacturing a brake shoe assembly, it is necessary to separately form a segment of friction material and thereafter attach it to a supporting structure.
In view of the above, it is a principal aspect of this invention to provide a brake shoe assembly which may be produced at lower cost as compared to currently available brake shoe assemblies. It is another aspect of this invention to provide a brake shoe assembly featuring excellent mechanical engagement between the friction material and the brake shoe.
The above principal aspects of this invention are provided by an assembly constructed by a process involving casting friction material directly onto a metal brake shoe or to a backing plate which includes a plurality of perforations and raised tabs which cause an interlocking engagement to occur between the friction material and the supporting structure. In accordance with the teachings of this invention, the perforations and raised tabs are formed by cutting a portion of the brake shoe or backing plate and bending a tab portion formed within the area of the cut.
Casted brake shoe assemblies have been previously proposed and a list of such references teaching such techniques are listed below.
______________________________________ U.S. PAT. NO. INVENTOR DATE ______________________________________ 1,880,750 T. F. Brackett October 4, 1932 1,937,140 W. A. Blume November 28, 1933 1,927,252 W. H. Winters September 19, 1933 2,650,022 J. C. McCune October 20, 1953 1,872,850 M. N. Trainer August 23, 1932 2,948,361 R. B. Pogue August 9, 1960 ______________________________________
These references, however, do not teach the novel aspects of the brake shoe assembly and method according to this invention.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates upon a reading of the described preferred embodiments of this invention taken in conjunction with the accompanying drawings.